The invention relates to a circuit for controlling the frequency of a pulse generator associated with a microprocessor, wherein the microprocessor is connected to power line frequency and a frequency-determining element in form of an RC-stage is connected ahead of the pulse generator.
Microprocessors are provided with a pulse generator for determining the timed sequencing of the program. If a program with an exact maintenance of the sequencing is required, then a pulse generator must be used having a quartz crystal as the frequency-determining element. Contrary thereto, in case of a program where the timing sequence is unimportant or at least not critical, a pulse generator can be used having an RC-stage as the frequency determining element which, incidentally, is temperature sensitive. The quartz crystal operates very precisely, but it is relatively expensive. In contrast thereto, the RC-stage operates very imprecisely, but it is very inexpensive. Further a simple replacement of the two aforementioned components can readily be employed to change the timed sequence of the program, which is particularly of disadvantage when the circuit is used in a coin-operated game device wherein the timing sequence must be exactly maintained.